Michel Montignac worked for the greater part of his life as an international executive for the pharmaceutical industry.

At the beginning of the 1980s, while he was at the R&D (Research and Development) Center of the company he worked for in the USA, he undertook research on existing scientific publications on nutrition and diabetes. He took a particular interest in the studies published in 1976, 1977 and 1981 by P.A. Crapo, a Stanford University diabetes expert.

Crapo’s studies show that (an innovative finding at the time), contrary to widespread belief of the times, carbohydrates were not interchangeable. That is to say that, carbs with equal amounts of pure sugar content did not necessarily have the same impact on blood sugar levels (glycemia) after meals; that their effect could differ, and differ greatly regardless of whether they were complex or simple glucids.

Crapo thus suggests that a diet based exclusively on carbs with a low potential to increase blood sugar levels could serve as therapy for controlling diabetic glycemia.

Michel Montignac, who did not suffer from diabetes but was simply overweight, decided to try this diet after having observed that 85% of the people who had diabetes were also obese. After having lost over 30 pounds in three months without depriving himself of calories, he opted for continuing his research along this line.

He then discovered that a Canadian researcher, David Jenkins, had together with Crapo’s research, endeavored to design a hierarchical model which established the glycemic potential of carbohydrates with reference to a standard value. The reference chosen was glucose to which he arbitrarily assigned a value of 100. Each carb was thus assigned a corresponding Glycemic Index.

As of 1986, Michel Montignac was already proposing in his books and publications a weight-losing method which used Glycemic Indexes to guide the choice of carbs for people wanting to lose weight and stay slim. Considering the lack of knowledge at the time, Montignac restrained from filling his books with scientific and technical data which might confuse the issue and limited himself to classifying carbs into "bad glucids”, as those which should be avoided and “good carbs”, as those which should be preferred by people wishing to lose weight.

Montignac suffered violent attacks from official nutritionists who sustained that his method was "Manichean and out of focus". In view of the fact that nutritionists intentionally misinterpreted his layman classification of "bad and good carbohydrates", in 1991 Michel Montignac decided to go into the scientific details and principles of his method in all of his books and publications.

Michel Montignac was a pioneer in the use of Glycemic Indexes to lose weight. His use of this concept is detailed in The Glycemic Index Concept.